Fissure is a crack in a rock. Certain fissures date back to the formation of the rock, others are the result of tectonic forces that have subsequently acted on it.

Those of compact and hard rocks are called joints. They are due to tensile, torsional or compressive stresses. Temperature changes and weathering highlight and expand the width of joints, fractures and sedimentation planes, and in carbonate rocks dissolution also intervenes in this process as the main agent.[1]​.

Contraction or shrinkage cracks or fissures are produced by the drying of clay material or by the cooling of volcanic rocks (columnar disjunction).